Influvac (influenza vaccine)

How does it work?

Influvac is a vaccine against seasonal flu (influenza). It works by provoking the body's immune response to the flu virus, without actually causing the illness.

When the body is exposed to foreign organisms, such as viruses and bacteria, the immune system produces antibodies against them. Antibodies help the body recognise and kill the foreign organisms. They then remain in the body to help protect the body against future infections with the same organism. This is known as active immunity.

The immune system produces different antibodies for each foreign organism it encounters. This establishes a pool of antibodies that helps protect the body from various different diseases.

Vaccines contain extracts or inactivated forms of bacteria or viruses that cause disease. These altered forms of the organisms stimulate the immune system to produce antibodies against them, but don't actually cause disease themselves. The antibodies produced remain in the body so that if the organism is encountered naturally, the immune system can recognise it and attack it, thus preventing it from causing disease.

Each virus or bacteria stimulates the immune system to produce a specific type of antibody. This means that different vaccines are needed to prevent different diseases.

Influenza vaccines stimulate the immune system to produce antibodies against the virus that causes flu. The flu virus, however, is constantly changing its structure (mutating). This means that each year a different vaccine containing different strains of the virus is needed. Influvac contains three different strains of the flu virus that have been identified by the World Health Organisation and the EU as being prevalent for the 2014 to 2015 season. These are an H1N1 strain of influenza A, an H3N2 strain of influenza A and a strain of influenza B.

Influenza vaccination should be repeated each year before the start of the flu season with the
appropriate, approved vaccine. Protection against flu usually occurs within two to three
weeks after vaccination. The length of the protection varies, but usually
lasts 6 to 12 months.

What is it used for?

Prevention of
seasonal flu
(influenza) in adults and children aged six months and over.

A seasonal flu vaccine is recommended for people who run an
increased risk of complications, such as pneumonia or being admitted to hospital, if they get flu.

These people include those aged over 65 years, people living in long-stay residential care homes,
pregnant women and anyone older than six months of age with one or more of the following conditions: chronic lung
disease, including asthma; chronic kidney, liver, heart or neurological disease;
diabetes; HIV infection; or an underactive immune system, either due to disease
or treatment. People who live with someone who has an underactive immune system are also advised to have a flu vaccine, as are carers and healthcare workers who are involved in direct patient
care.

The Department of Health has also recommended that children aged two to 17 years who are otherwise healthy should be included in the flu vaccination programme. Children will be given a new vaccine called Fluenz, which is administered by nasal spray. Follow the link at the end of this page for more information.

How is it given?

The vaccine should be given each year before the start of the flu season (the best time to have it is from September to early November).

For adults and older children the vaccine is usually given as a single injection into the muscle of the upper arm. For infants and younger children the thigh is the preferred site.

The vaccine may also be given under the skin (subcutaneously).

Children aged six months to less than nine years who have not previously been vaccinated against
flu should be given a second dose of the vaccine at least four
weeks after their first vaccination. Children who have previously had a flu vaccine only need one dose.

Warning!

This vaccine will only protect against flu caused by
the strains of the influenza virus that are closely related to those found in the vaccine. It will not prevent flu-like illnesses caused by other
germs.

People who have an underactive immune system, for example due to a genetic defect, disease such as HIV infection, or treatment with immunosuppressant medicines such as chemotherapy, high-dose corticosteroids, or immunosuppressants, eg used following an organ transplant, may not produce an adequate number of antibodies in response to this vaccine. As a result, the vaccine may be less effective in these people.
Discuss this with your doctor.

Not to be used in

People with feverish illness or infection. (The vaccine should be postponed until after recovery).

People who have previously had a serious allergic reaction (anaphylaxis or severe asthma attack) to eggs or chicken protein.

People who have previously had a serious allergic reaction (anaphylaxis) to the antibiotic gentamicin.

People who have previously had a serious allergic reaction (anaphylaxis) to formaldehyde, cetyltrimethylammonium bromide or
polysorbate 80.

This vaccine is not recommended for children under six months
of age because its safety and effectiveness have not been studied in this age group.

This vaccine should not be used if you are allergic to one or
any of its ingredients. Please inform your doctor or pharmacist if you have
previously experienced such an
allergy. If you feel you have
experienced an allergic reaction after having this vaccine, inform your doctor or pharmacist
immediately.

Pregnancy and breastfeeding

Certain vaccines should not be used during pregnancy or
breastfeeding. However, other vaccines may be safely used in pregnancy or
breastfeeding providing the benefits to the mother outweigh the risks to the
unborn baby. Always inform your doctor if you are pregnant or planning a
pregnancy, before having any vaccine.

There are no known harmful effects when this vaccine is given to pregnant women. Flu vaccination is recommended for all pregnant women.

There are no known harmful effects when this vaccine is given
to breastfeeding mothers.

Side effects

Vaccines and their possible side effects can affect individual
people in different ways. The following are some of the side effects that are
known to be associated with this vaccine. Just because a side effect is stated
here does not mean that all people having this vaccine will experience that or
any side effect.

This vaccine contains no live virus and cannot cause flu.

Common (affect between 1 and 10 out of every 100 people)

Headache.

Sweating.

Pain in the muscles and joints.

Fever (pyrexia).

A general feeling of being unwell (malaise).

Shivering.

Fatigue.

Pain, swelling, redness and hardening of the skin at the
injection site.

Bruising at the injection site.

These reactions are due to the immune system responding to the vaccine and are not flu. They usually disappear within one to two days without treatment.

The side effects below have been reported from post-marketing surveillance. The frequency of these side effects is unknown.

Swollen glands.

Rash or itching.

Allergic reaction to active ingredient.

Pins and needles (paraesthesia).

Seizures (convulsions).

Neurological disorders, such as encephalomyelitis and neuritis.

Inflammation of blood vessels (vasculitis).

Temporary decrease in the number of platelets in the blood (thrombocytopenia).

The side effects listed above may not include all of the side
effects reported by the vaccine's
manufacturer. For more
information about any other possible risks associated with this vaccine, please
read the information provided with the vaccine or consult your doctor or
pharmacist.

How can this vaccine affect other medicines?

This vaccine is not known to affect other medicines.

However, people taking medicines that suppress the activity of the immune system, for example chemotherapy, high-dose corticosteroids, or immunosuppressants used following an organ transplant, may not produce adequate numbers of antibodies in response to this vaccine. As a result, the vaccine may be less effective in these people.
If you are taking any of these medicines you should
discuss this with your doctor.

This vaccine may be given at the same time as other vaccines,
but if so, the vaccines should be given into different limbs.

The materials in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site does not have answers to all problems. Answers to specific problems may not apply to everyone. If you notice medical symptoms or feel ill, you should consult your doctor - for further information see our Terms and conditions.